Pressing it will call the emergency services and provide them with personal details -- including an image -- plus GPS coordinates, and will activate the phone's camera and microphone too for good measure.

A sliding/locking mechanism ensures that the alert button is pretty much impossible to press by accident, but when the button is needed, it calls for help silently.

The polycarbonate case, which supports the iPhone 4, 4S, 5 and 5C, also serves as a straightforward smartphone case and one that will hopefully never be needed to protect anything other than the device itself.

However, the Lifesaver Case, which this week launched a crowd-funding campaign via Indiegogo has already received strong and vocal support from a host of US organizations including the National Coalition Against Domestic Violence.

The company's founder, Jon Powell has already invested over $100,000 of his own money and two years of his life into making the concept a reality and is hoping to raise a final $100,000 over the next month in order to bring the case to market in the US by August.

He also hopes that if the funding target is achieved that the Lifesaver case will eventually retail for $100 although there is an early-bird backer offer of $59 limited to the first 500 cases.

The system works via an app into which the user will enter his or her details and the app then runs on the phone in a permanent standby mode so that it draws little or no power from the phone's battery, only launching properly when the alarm is raised.

Because it calls e911 or NG911, the US-enhanced and next-generation emergency services in the case of trouble, it can transfer digital data, meaning that there is no need to speak to an operator.

However, because these next-generation systems are not yet global, the company currently has no plans to roll the case out beyond its native U.S.